Guanidine and urea both belong to a small class of organic molecules called osmolytes, which have been studied extensively because they play an important role in biological functionality.  Urea is known to denature proteins while guanidine promotes their stability.  Both molecules contain many sites for hydrogen bonding, and interactions with water are certainly important to their biological functionality and their abilities to influence protein stability.   To begin to understand how both guanidine and urea affect the hydrogen bonded network of water, optimum geometries and the corresponding vibrational frequencies of networks of guanidine, urea, and water have been computed using density functional theory.  The DFT functionals employed are Becke’s three-parameter hybrid functional using the LYP correlation functional, the M06-2X high nonlocality hybrid functional from Thular and Zhao, and the ωB97XD functional from Head-Gordan and coworkers which includes empirical dispersion.  The basis sets employed are two of Dunning and coworkers’ correlation consistent basis sets with diffuse functions: aug-cc-pVDZ and aug-cc-pVTZ.<br/>

Noncovalent interactions in networks of guanidine, urea, and water

255th National Meeting (2018)

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